1. Field of the Invention
This invention relates to an encapsulant composition having a superior moisture resistance and also having good continuous operability and reflow resistance, and an electronic device having device components encapsulated with this composition.
2. Description of the Related Art
In recent years, with an improvement in integration of semiconductor device components such as ICs (integrated circuits) and LSIs (large-scale integrated circuits), device components are being made larger in scale and semiconductor devices are being made smaller and thinner. In thin-type semiconductor devices, however, the occurrence of blistering or cracking in their production steps has come into question. This is because, when semiconductor devices are mounted to a substrate, they are exposed to a high temperature of 200.degree. C. or above in a short time as a result of their immersion in a soldering bath, so that the moisture contained in an encapsulant vaporizes and the vapor pressure thereby produced acts as a peel stress at the interface between the encapsulant and a insert such as the device component or a lead frame to cause separation of the encapsulant from the insert at their interface.
As measures for preventing the blistering or cracking caused by such separation, used are a method in which a coat material is used on the device surface or the back of islands of a lead frame so as to improve its adhesion to the encapsulant, a method in which dimples or slits are formed on the back of islands of a lead frame, and a method in which an LOC (lead on chip) structure is employed so as to improve the adhesion to the encapsulant. These methods, however, have the problems that a high cost may result or no satisfactory effect can be attained. Accordingly, it is sought to improve the encapsulant itself.
Under such circumstances, as a measure for improving the adhesion between the encapsulant and the insert, the manner of addition of and treatment with various coupling agents has been studied on, e.g., making epoxy resins and curing agents have lower viscosity (lower molecular weight), using epoxysilane and mercaptosilane in combination, and using ureidosilane and mercaptosilane in combination. These conventional methods, however, can not be said that they provide sufficient adhesion between the encapsulant and the insert. Moisture may enter from slightly separated portions to cause the problem of a low moisture resistance.